In the field of the gymnastic machines the use of gravitational load groups is well known, wherein the resistive action against the physical activity of a user is exerted by one or more load elements, for instance metallic bodies usually indicated as “weights” or “bricks”, moved against the action of the gravitational force. As used herein, the term “gymnastic machine” is equivalent to “exercise machine”. A gravitational load group of the known type is illustrated in FIG. 1 just by way of example. As used herein, the term “gravitational load group” is equivalent to “weights” or “bricks”. This load group comprises vertical guides carried integrally by a respective frame, and a movable equipment consisting of a support member, often indicated as “spider”, and two or more weights carried in a freely sliding manner by the vertical guides and stably connected to the respective support member. In particular, the support member comprises a head portion, arranged at the top, and a coupling portion, constituted by a bar presenting a plurality of substantially horizontal first holes arranged in a stepped manner. Similarly, each weight presents a substantially horizontal second through hole so that it is possible to couple to the spider a number of weights, and therefore a resistive load, that can be selected by the user substantially at will simply inserting a blocking pin in this second hole and in the first corresponding hole. In use, the head portion of the coupling member of the weights is connected to a respective interface, for example a gymnastic implement, through a mechanical transmission group, so that the actuation of this interface by a user of the respective gymnastic machine can occur against the resistance exerted by lifting the movable equipment of the gravitational load group. Referring to FIG. 1 just by way of example, this transmission group comprises a traction cable maintained tensioned between a plurality of return members, generally constituted by pulley.
At this point it should be noted that the known gravitational load groups, as that illustrated in FIG. 1, present drawbacks entailing the risk of injuries for the users of the respective gymnastic machines. These drawbacks are particularly evident when a user uses reduced loads for executing physical exercises involving at least one series of fast repetitions of a given athletic movement. Actually, under these training conditions, when a user performs an exercise particularly intensely and very fast, the movable equipment picks up high speed and tends to follow a substantially inertial ascending motion, i.e. it is subjected to a vertical ascending displacement along the respective guides that continues also when the action exerted by the user on the respective interface ends. This substantially inertial ascending motion can be also defined as a motion without synchronicity between the exertion by the user of a force on the interface and the movement of the movable equipment along the respective vertical guides. It should be noted that, in the presence of these substantially inertial motions of the movable equipment of the load group, two different drawbacks can occur, in succession or independently one of the other: first of all, the movable equipment, continuing rising, can impact against the frame portion acting as a stop for the guides. In addition to cause noise, extremely unpleasant for a user who wants to focus on the execution of the respective physical exercises, this circumstance can clearly lead to an undesired damage of the load group and/or of the transmission group connecting it to the respective interface. In addition to this, it should be noted that, following each substantially inertial ascending displacement, the movable equipment is subjected to a descending motion in substantially free fall, usually ending with a sudden and unexpected tension of the respective traction cable, and therefore with the transmission of a force pulse along this cable. This impulsive action can achieve the user, who will be subjected to a sharp and unexpected traction by the respective interface. This traction is generally felt by the user as a recoil coming from the load group, and can cause not only an interruption or an unbalance in executing the physical exercises, but also an undesired injury of the user's body portion involving the respective interface.
In view of the above description it is therefore clearly apparent that the use of known gravitational load groups in the gymnastic machines entails drawbacks that have been not still addressed and that are potentially dangerous for the users of these machines. In particular, the problem of having available a safety device for gravitational load groups usable to prevent substantially inertial ascending motions of the movable equipment while executing physical exercises is currently unsolved. In more detail, it would be desirable to have available a safety device which allows a movable equipment to translate freely upwards along the respective guides when it is subjected to the action exerted by a user, but which prevents, or at least minimises, any further ascending displacement of the movable equipment after the end of the action exerted by this user.